A comparison study of two methods of peanut agglutinin staining with S100 immunostaining in 29 cases of histiocytosis X (Langerhans' cell histiocytosis)

Staining with peanut agglutinin (PNA) and with polyclonal antibody to S100 protein have both been recommended as aids in the diagnosis of histiocytosis X (Langerhans' cell histiocytosis). Although a large body of literature attests to the utility of S100 staining in this condition, the few published studies that involve PNA staining have employed varying methods of radically different results. We studied formaldehyde solution-fixed, paraffin-embedded tissue from 29 cases of histiocytosis X by using standard avidin-biotin immunostaining for S100 protein, as well as two published methods of PNA staining. All cases stained positively for S100 protein. By utilizing prior trypsinization and a three-step procedure, all cases also stained with PNA. With a two-step PNA-staining procedure, however, 9 cases failed to stain with PNA, and 3 cases showed a diffuse staining pattern that was not considered characteristic of Langerhans' and histiocytosis X cells. We concluded that both the S100 and the three-step PNA procedures are sensitive methods for the diagnosis of histiocytosis X.